<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .main{
            width: 100%;
            height: 100px;
        }
        .left{
            width: 20%;
            height: 100px;
            float: left;
            text-align: center;
            line-height: 100px;
            background-color: blue;
        }
        .middle{
            width: 25%;
            height: 100%;
            text-align: center;
            line-height: 100px;
            float: left;
            background-color: green;
        }
        .right{
            /* width: 100%; */
            margin-left:45%;
            text-align: center;
            line-height: 100px;
            background-color: red;
            height: 100px;
            padding-right: 10px;
        }
    </style>
</head>
<body>
    <div class="main">
        <div class="left">
            left
        </div>
        <div class="middle">
            middle
        </div>
        <div class="right">
            right
        </div>
    </div>
</body>
</html>